TA 
581 


IC-NRLF 


TlLUSTRATED  CATALOGUE 

A  X— - «*•«•• 


Of» 


ENGINEERING,  SURVEYING 
AND  SCIENTIFIC 

INSTRUMENTS 


Sfreet,    .*%  .",  ST.  LOUIS,  MO, 


, 


George  Davidson  182^-1911 


ENGINEERING.SURVEYING 
AND  SCIENTIFIC 

INSTRUMENTS 


yw/\HN  &  co., 

i  » 
212  Locust  Street,     .".    .".    ST.   LOUIS,   MO. 


'_    . 


m 


INTRODUCTION. 


received    many    applications   for  Catalogues 

~s    and  Cuts  of  our  Instruments,  we  have  issued  this  pam- 
phlet,  pending  the  preparation  of  a  more  complete 
Catalogue. 

We  must  say,  however,  that  with  our  superior  facilities, 
consisting  of  the  latest  and  most  improved  machinery  and 
tools,  with  the  advantages  of  steam  power,  large  practical 
and  technical  experience,  we  are  enabled  to  compete  with 
the  best  makers  in  quality  of  work  as  well  as  in  prices. 

To  our  patrons  who  have  favored  us  with  their  orders 
we  give  our  sincerest  thanks  ;  and  to  our  patrons,  present  and 
future,  we  give  our  word  never  to  cease  to  have  every  pos- 
sible care  taken  in  order  not  to  allow  any  instrument  to  leave 
our  Factory  unless  we  can  guarantee  its  perfection  in  every 
particular  ;  and  we  say  with  some  complacence  that  our 
Factory  has  the  means  to  compete  with  makers  of  world- 
wide fame. 

We  are  very  confident  that  hereafter  Western  Engineers, 
Colleges,  and  other  Educational  Institutions  need  not  go 
further  for  their  instruments  ;  for  in  prices,  as  well  as  in 
quality,  we  are  enabled  to  compete  with  the  oldest  and  best- 
known  factories  in  the  eastern  market. 

We  do  not  claim  to  make  a  very  cheap  instrument;  it  is 
a  fact  well  known  to  us  that  there  are  in  the  market  instru- 
ments made  only  to  sell,  and,  as  to  precision,  have  nothing 
but  the  name.  These  instruments  are  sold  at  prices  low 
enough,,  but  there  is  not  a  surveyor  or  engineer  who  does 
not  know  how  many  are  the  inconveniences,  damages,  and 
losses  of  time  which  are  invariably  the  result  of  their  faulty 
construction. 


Our  experience  and  pride  forbid  us  to  enter  into  compe- 
tition with  these,  but  if  our  prices  are  compared  with  the 
lists  of  the  best  makers,  a  good  saving  is  apparent ;  and  as 
for  quality,  in  order  to  justify  our  claim,  we  do  not  hesitate 
to  send  our  responsible  patrons  the  instruments  for  inspec- 
tion, trial,  or  comparison,  in  order  to  enable  them  to  form 
their  own  judgment. 

The  suggestions  of  our  patrons  will  always  be  cheerfully 
accepted  as  the  result  of  an  experience,  which,  to  the  con- 
structor, sometimes  may  pass  unobserved.  One  of  these 
suggestions,  after  careful  consideration,  has  led  us  to  con- 
struct a  middle-weight  (about  7  pounds)  transit,  for  mining, 
mountain  and  prospecting  work,  which  we  really  believe  is  far 
superior  to  anything  made  for  the  same  purpose  to-day.  All 
suggestions  of  the  experienced  engineer,  with  the  careful 
consideration  of  the  constructor,  cannot  fail  to  give  good  re- 
sults, and  we  are  always  sincerely  pleased  to  accept  the  judg- 
ment of  those  whose  experience  qualifies  them  to  give  wise 
counsel.  Besides  our  transit-theodolites,  transits,  levels, 
etc.,  we  make  to  order  every  variety  of  scientific  as  well  as 
geodetic  instruments,  as  will  be  seen  further  on  in  this  pam- 
phlet, at  prices  as  low  as  consistent  with  the  quality  of  our 
work. 

REPAIR     OF     INSTRUMENTS. 

We  undertake  the  repairing  of  instruments  of  other 
makers  as  well  as  our  own ;  except  for  instruments  of  our 
own  and  other  first-class  makes,  we  hold  ourselves  respon- 
sible for  our  work  only,  as  there  are  many  inferior  instru- 
ments which  cannot  be  made  perfect,  and  the  firm  that 
repairs  them  is  oftentimes  censured  for  faults  original  with 
the  constructor.  To  these,  however,  we  will  guarantee  the 
best  that  can  possibly  be  done. 


Our  patrons  will  please  specify  which  parts  they  wish  to 
have  repaired ;  for  it  is  customary  in  our  shop,  whenever 
there  are  no  specified  orders,  to  make  all  the  repairs  neces- 
sary to  put  the  instrument  in  good  working  order. 

ASTRONOMICAL     INSTRUMENTS. 

As  is  well  known,  these  instruments  are  made  to  order 
only,  each  customer  having  ideas  of  his  own,  to  which  the 
constructor  must  adhere,  to  give  satisfaction.  For  this  reason, 
it  is  very  difficult  to  give  correct  descriptions  of  these  instru- 
ments and  their  prices.  In  this  pamphlet  we  have  omitted 
descriptions  and  cuts,  reserving  them  for  our  future  larger 
and  more  complete  Catalogue.  We  only  wish  to  make  it 
known  that  we  have  means  and  machinery  powerful  enough 
to  construct  Astronomical  Instruments  of  every  size  now 
used,  and  estimates  for  such  will  be  cheerfully  given. 

MAHN    &    CO. 


\  I/E  refer,  by  permission,  to 


PROF.  J.  B.  JOHNSON, 

Washington  University, 

ST.  Louis,  Mo., 

AUTHOR  OF  THEORY  AND  PRACTICE  OF  SURVEYING, 
who  has  kindly  consented  to  reply  to  any  inquiries  con- 
cerning the  character  of  our  work. 


NOTICE. 

fT  is  not  our  aim  to  take  up  space  in  this  pamphlet  to 
describe  the  various  adjustments  of  instruments,  for  every 
Engineer  and  Surveyor  can  find  these  in  all  standard  works 
on  surveying,  notably  in  THEORY  AND  PRACTICE  OP^  SUR- 
VEYING, by  Prof.  J.  B.  Johnson.  We  limit  ourselves,  there- 
fore, to  a  few  hints  on  keeping  instruments  in  good  order, 
for  the  benefit  of  young  Engineers,  those  more  experienced 
not  needing  such  directions. 

CARE     OF     INSTRUMENTS. 

1.  In  using  your  instrument  in  the  field,  be  sure  that  the 
legs  of  its  tripod  are  firm  ;  not  too  loose  and  not  too  tight ; 
this  may  easily  be  determined  by  raising  one  leg  at  a  time 
to  a  horizontal  position,  and  then  letting  it  fall ;   if  it  falls 
abruptly,  it  is  too  loose  ;  and  if  it  does  not  fall,  it  is  too  tight ; 
to  be  right  it  must  descend  slowly  and  easily  to  the  ground. 
Do  not  use  the  instrument  before  ascertaining  that  it  is  set 
firmly. 

2.  Do  not  play  with  the  needle,  especially  with  iron  or 
steel,  and  always  screw  it  well  up  against  the  compass  glass 
when  not  in  use.     In  reading  the   needle,  do  not  use  mag- 
nifying glasses  mounted  in  hard  rubber  frames. 

3.  If  any  unusual  resistance  is  felt  in  the  centers  or  object 
slide  of  Telescope,  take  them  out  and  endeavor  to  smooth 
the   roughened  part  with  a  piece  of  smooth  hardened  steel, 
like  the  back  of  a  pocket-knife,   etc.  ;   in  taking  the  centers 
apart,  be  sure  to  remove  all  the  springs  from  spring  boxes 
opposing  tangent  screws,  thus  leaving  them  free. 


8 

4-     If  any  of  the  screws  exposed  to  dust  work  hard,  clean 
them  well  with  a  stiff  tooth  brush. 

5.  Do  not  grease  any  of  the  parts  exposed  to  dust,  but 
keep  them   clean ;   if    any   lubricating,    however,  is    found 
necessary  on  the  screws,  use   a  little  oil,  work  the  screws 
back  and  forth  a  few  times  and  then  clean  them.     Be  very 
careful  in  oiling    all  the  parts,  and  more   particularly   the 
centers,  not  to    apply  the  new  oil  before  having   entirely 
cleansed  the  parts  of  all  old  oil  and  dust.   This  can  be  done 
by  wetting  pieces  of   muslin  with  benzine,  or  new  oil,  and 
using  until  they  remain  clean  after  rubbing  well  all  parts. 
For  lubricating  we  would  prefer  rendered  marrow,  because 
it  does  not  gum,  but  in  our  latitude  fine  watch  oil  is  found 
preferable,  as  it  does  not  freeze. 

6.  Proceed  in  the  same  manner  if  the  resistance  is  found 
to  be  on  the  Telescope  axis  or  clamp,  and  always  be  sure 
to  remove  spring  from  spring  box  before  trying  to  take  it 
apart. 

7.  If  the  glasses  of  Telescopes  are  dull  and  filmy,  take 
them  out  and  clean  them  with  a  piece  of  fine  chamois  skin 
or  fine  muslin,  wetted  with  alcohol  (spirits  of  wine)  ;  dry 
them  with  a  piece  of  fine,  clean  muslin  or  linen,  and  brush 
them  with  a  fine,  clean  camel's  hair  brush,  to  remove  any  pos- 
sible dust  left  by  the  muslin,  and  then  replace  them  in  proper 
position.      The   object  glass  should  not  be  cleaned  oftener 
than  necessary,  as,  in  removing  and  replacing  it,  its  adjust- 
ments are  likely  to  be  disturbed.      It  is  oftentimes  sufficient 
to  clean  the  front  glass  and  the  glass  nearest  the  eye  in  the 
ocular  or  eye  piece  without  removing.     The  ocular  is,  how- 
ever, not  so  susceptible  to  disarrangement,  and  can  be  taken 
out  and  replaced  as  often  as  desirable.     To  do  this  in  our 
instruments,  it  is  only  necessary  to  loosen  the  top  screw  at 
the  end  of  the  main  tube,  directly  over  the  ocular.     To  clean 


the  glasses  with  a  silk  handkerchief  is  not  only  undesirable, 
but  objectionable. 

8.  To  clean  graduations  on  solid  silver,  should  they  hap- 
pen to  oxidize  after  using  instruments  in  sewers  or  places 
where  they  are  exposed  to  the  action  of  acids  or  gases,  rub 
them  gently  with  a  piece  of  chamois  skin  or  linen  wetted  with 
fine  oil,  until  clean,  taking  great  care  of  the  edges  of  the  grad- 
uations, in  order  not  to  spoil  their  fineness.  This  is,  however, 
a  very  critical  operation  that  should  never  be  resorted  to 
except  when  absolutely  necessary,  and  then,  if  practicable, 
by  a  maker  only. 

All  the  above  and  a  few  other  minor  inconveniences  may 
be  remedied  by  the  Engineer  or  Surveyor.  Should  any- 
thing else  happen,  a  reputable  maker  should  be  resorted  to. 

After  an  instrument  has  had  a  fall,  if  any  of  its  parts  are 
found  stiff,  and  do  not  yield  to  the  touch  of  the  hand  as 
easily  as  before,  it  should  not  by  any  means  be  forced,  but 
sent  as  it  is  to  a  maker.  If  any  parts,  centers,  plates,  or 
axes  are  sprung  or  bent  by  the  fall,  if  forced,  they  may 
press  against  the  graduations  hard  enough  to  render  them 
completely  useless,  while,  if  left  unused,  they  may  be 
repaired  at  a  very  small  expense. 

Too  much  care  cannot  be  taken  or  recommended  in  this 
particular. 

GRADUATIONS. 

The  graduations,  together  with  the  telescope,  have  been 
justly  termed  the  soul  and  brain  of  an  instrument. 

We  guarantee  these  to  be  accurate,  the  severest  test  in 
the  field  having  thus  far  failed  to  find  any  appreciable 
errors.  The  lines  are  perfectly  straight,  black,  and  uni- 
form. All  of  our  transits  have  two  double  verniers,  as 


10 

seen  in  the  cuts.  They  were  often  placed  at  an  angle  of 
30  degrees  to  enable  the  engineer  to  read  a  vernier  without 
changing  the  position  after  sighting.  Covers  of  fine  glass 
protect  the  verniers  from  exposure,  and  two  plates  of 
ground  glass  cast  a  very  clear  light,  which  enables  the  read- 
ings to  be  made  with  great  ease. 

The  graduations  are  either  on  brass  silver-washed,  or 
on  solid  silver  for  the  finest  instruments. 

TELESCOPE. 

This  most  important  part  of  a  good  instrument  we  guar- 
antee to  be  the  best  made.  We  really  claim  to  make  the 
best  Telescopes,  and  without  going  into  small  details  of 
construction  (found  in  every  Engineer's  handbook),  we 
leave  it  to  our  patrons  themselves  to  judge,  after  comparing 
ours  with  any  of  the  best  makers  they  may  wish. 

Comparisons  are  said  to  be  odious,  but  it  cannot  be 
denied  that  they  are  sometimes  instructive. 

Our  experience  also  has  taught  us  a  judicious  method  of 
construction,  by  which  we  are  enabled  to  guarantee  their 
correctness  at  all  distances.  All  Telescopes  have  a  pro- 
tection over-slide,  although  in  some  it  is  not  shown  in  the 
cuts. 

SPIRIT    LEVELS. 

Our  spirit  levels  are  carefully  ground  and  thoroughly 
tested  in  our  shop. 

The  finest  levels  for  astronomical  instruments  we  provide 
with  an  air  chamber  for  the  regulation  of  the  length  of  the 
bulb,  but  this  is  not  necessary  in  surveying  instruments 
generally.  We  grind  our  glasses  according  to  the  grade  of 
the  instrument,  and  we  guarantee  all  of  them  to  have  a 
uniform  curvature. 


11 


ILLUMINATING  OF    CROSS  WIRES. 

When  desired  we  make  at  a  small  extra  expense  an 
arrangement  to  illuminate  cross  wires.  The  system  is  about 
the  same  as  used  in  astronomical  instruments,  and  very 
easy  to  operate. 

SHIFTING     CENTERS. 

All  of  our  Transits  and  Theodolites  have  the  shifting 
centers,  and  at  a  small  extra  expense  we  can  attach  to  them 
a  quick-leveling  attachment;  this  can  also  be  attached  to  all 
our  Levels. 

CLOTH     FINISH. 

We  are  prepared,  when  desired,  to  give  to  our  instru- 
ments what  is  termed  a  cloth-finish.  We,  however,  frankly 
say  that  we  do  not  admire  this  finish,  as  it  looks  decidedly 
ugly  as  soon  as  the  newness  is  gone.  Furthermore,  it  has 
no  advantages  over  any  other  finish,  as  we  know  by  long 
experience.  We  like  our  finish  much  better,  as  being  finer, 
prettier,  and  lasting  longer. 

GENERAL     CONSTRUCTION. 

In  conclusion,  we  must  say  that  the  general  construction 
of  our  instruments  is  the  result  of  many  years  of  experi- 
ence and  study. 

In  our  experience  in  Europe  and  America,  we  had  the 
opportunity  to  study  all  the  best  makers,  and  as  a  result  we 
adopted  a  system  that  we  can  thoroughly  recommend.  We 
allow  superiority  to  no  one.  The  metal  adopted  is  very 


12 

hard,  unyielding  brass  and  bell  metal.  We  gave  aluminum 
and  the  kindred  metals  due  attention,  and,  except  for  a  few 
of  the  minor  parts,  we  do  not  recommend  it.  All  of  our 
transits  have  long,  very  hard,  unyielding  centers,  perfectly 
concentric ;  a  very  hard  telescope  axis,  and  all  other  parts 
harder  than  are  commonly  used. 

Our  Levels  have  either  very  hard,  bell-metal  or  steel  cen- 
ters, and  bell-metal  collars  in  wyes. 

SCIENTIFIC     INSTRUMENTS. 

Persons  who  consult  this  pamphlet  will  see  cuts  of  some 
scientific  instruments  which  we  have  manufactured  from  the 
designs  of  the  inventors,  among  whom  may  be  mentioned 
Professor  J.  B.  Johnson  and  Mr.  B.  H.  Colby,  of  this  city. 

Prof.  J.  B.  Johnson  does  not  need  to  be  introduced,  as 
we  believe  there  is  not  another  person  more  or  better  known 
to  the  engineering  profession. 

Mr.  B.  H.  Colby  is  the  chief  Topographical  Engineer  of 
St.  Louis,  and  is  well  known  as  an  expert  topographical 
surveyor. 

We  are  the  sole  manufacturers  of  these  instruments. 

GENERAL     REMARKS. 

Our  firm  being  comparatively  new,  our  cuts  are 
somewhat  limited.  We  manufacture,  however,  many  sizes 
of  instruments  which  differ  from  the  cuts  in  size  only ;  we 
did  not  deem  it  necessary  to  have  cuts  of  all  sizes  made  for 
this  pamphlet ;  we  reserve  these  for  our  future  larger  Cat- 
alogues, and  for  the  present  content  ourselves  with  but  few 
descriptions. 


13 

We  have,  for  instance,  but  one  cut  of  a  Transit-Theodolite, 
while  we  manufacture  several.  One  of  a  Mountain  Transit, 
while  we  manufacture  two,  and  almost  all  of  our  Engi- 
neers' Transits  we  manufacture  in  two  sizes.  In  Transits 
the  difference  is  mostly  in  size,  while  in  Theodolites  it  is  in 
style  also. 

We  wish  also  to  make  it  known  that,  while  we  did  not 
deem  it  necessary  to  have  wood-cuts  made  for  illustration 
(they  all  being  well  known  and  nothing  new),  we  furnish 
the  profession  and  all  educational  institutions  with  every 
style  of  Rods,  Poles,  Chains,  Tapes — in  fact,  the  entire 
outfit — in  any  quantity  at  lowrest  prices  consistent  with  the 
quality  of  the  goods. 


Fig.  No.  I.-TRANSIT-THEODOLITE. 


TRANSIT-THEODOLITE. 

After  many  inquiries  for  instruments  capable  of  doing, 
in  the  highest  degree,  rapid  and  accurate  work,  and  com- 
bining at  the  same  time  lightness  and  portability,  and  after 
seeing  the  success  of  instruments  of  this  kind,  introduced 
into  this  country  by  one  or  two  of  the  best  makers,  we 
decided  to  design  one,  which,  we  feel,  is  an  improvement. 

We  manufacture  this  instrument  in  several  sizes — from 
five  to  eight  inches  diameter  of  horizontal  circle  -but  we 
mostly  recommend  our  seven-inch  as  being  the  most  con- 
venient for  lightness  and  portability,  and  experience  has 
shown  it  to  be  large  enough  to  admit  graduations  reading 
to  io/x,  by  verniers. 

When  the  plates  are  too  small  for  a  given  kind  of  grad- 
uation, it  makes  the  same  difficult  to  read,  as  two  or  more 
lines  over  the  vernier  appear  to  correspond  with  the  oppos- 
ing line  on  the  plate. 

This  instrument  is  provided  with  either  three  or  four 
leveling  screws,  as  may  be  desired ;  the  verniers  can  be 
placed  either  at  right  angles  with  the  line  of  sight,  or  at  an 
angle  of  30  degrees,  as  in  cuts ;  if  so  desired  they  can  easily 
be  placed  directly  in  the  line  of  sight. 

Complete  Transit-Theodolite  with  horizontal  circle,  6^ 
inches  in  diameter  ;  two  double  verniers  reading  2O/X;  vertical 
arc  or  circle  5  inches  in  diameter  ;  double  vernier  reading  to 
minutes  ;  two  reading  glasses  attached  to  instrument  to  read 
horizontal  limb  ;  and  one  attached  to  standards  to  read  ver- 
tical limb,  verniers  on  horizontal  plate  well  protected  by 
finest  plate  glass;  ground  glass  vernier  shades ;  n  to  12- 
inch  Telescope  (inverting  or  erect);  i^-inch  aperture, 
clear  and  powerful :  object  slide  well  protected  ;  reversible 


16 

clamp  to  Telescope  ;   compensating  tangent  screws  ;  gradi- 
enter  screw. 

Weight  of  instrument  complete,  about  13  Ibs.  ;  weight  of 
tripod,  about  7  Ibs. 

Mahogany  box  containing  sun  shade,  a  wrench,  a  screw- 
driver, a  plumb  bob,  and  several  adjusting  pins. 

Price,  complete  as  above $300  oo 

With  horizontal  limb,  7  inches  in  diameter,  and  verniers 
reading  iox/,  otherwise  same  as  above. 

Price,  complete $320  oo 

NOTE. — It  is  understood  that  instruments  of  this  class 
have  all  the  graduations  on  solid  silver.  The  above-quoted 
prices  are  for  instruments  with  three  leveling  screws  and 
fixed  stadia  wires. 


EXTRAS  TO    TRANSIT-THEODOLITES. 

Oblong  compass $   17  50 

Adjustable  stadia  wires 7  oo 

Five-inch  vertical  circle,  with  two  double  ver- 
niers, reading  30"  ;  attached  reading  glasses  ; 
graduation  well  protected X7  5° 

Level  attached  to  arm,  carrying  the  two  double 

verniers  of  vertical  circle J5  °° 

Striding  level  bearing  on  axis *7  5° 

*  Six-inch  striding  level  over  Telescope,  instead 

of   usual  fixed  level 25  oo 

*The   Striding   Level  over  Telescope  can  be  attached  either  when  the 
Telescope  is  normal  or  reversed. 


17 


ENGINEERS'   TRANSIT,   NO.   1  A. 

Transit  No.  1  A  is  shown  in  cut  No.  2  with  the  standards 
cloth  finished  ;  but,  as  we  explained  before,  we  do  not 
admire  this  finish,  and  do  not  recommend  it. 

This  instrument  has  been  designed  to  supply  the  want  of 
Engineers  wishing  a  well-made,  moderate-priced  instru- 
ment of  good  design. 

It  is  a  light,  very  strong,  and  well-made  instrument,  with 
all  the  latest  improvements. 

Horizontal  circle,  6^  inches  in  diameter;  two  double 
verniers  reading  to  30"  ;  verniers  protected  by  glass  plates  ; 
shades  over  verniers  ;  graduations  on  brass,  silvered  ;  radial 
clamps  with  compensating  tangents  ;  adjustment  for  the 
vertical  plane  of  Telescope  ;  the  Telescope  we  guarantee  to 
be  of  the  best,  1  1  inches  long,  clear  and  powerful  ;  object 
glass  with  i/4  -inch  clear  aperture;  objects  seen  erect. 

The  split-leg  tripod  is  considered  very  strong.  Its  legs 
are  of  the  best  ash,  and  the  tripod-head  a  strong  casting  in 
one  piece. 

Mahogany  box,  containing  sun  shade,  plumb  bob,  etc. 


Price,    plain     ............  $J^5  oo 

With  clamp  and  level  to  Telescope       .      .     .      .  175  oo 

Complete  with  vertical  arc  or  circle  reading  to 

minutes     ............  185  oo 


Fig.  No.  2.-ENGINEERS'  TRANSIT  No.  I  a. 


19 
EXTRAS  TO  ENGINEERS'  TRANSIT  NO.   1  A. 

Stadia  wires,  fixed $  3  oo 

Stadia  wires,  adjustable 10  oo 

NOTE. — To  those  preferring  it,  we  are  prepared  to  give 
this  instrument  a  black  or  green  finish  at  five  dollars  less 
than  its  regular  price.  It  must  not  be  inferred  by  this  that 
these  are  not  good  and  handsome  finishes  ;  the  contrary  is 
the  truth,  for  both  of  them  are  very  pleasing  to  the  eye ; 
they  are  finely  lacquered  and  wear  considerably  longer 
than  all  other  finishes  except  yellow,  and  are  very  much 
liked  by  all  who  have  seen  them.  Furthermore  the  green 
finish  is  very  pleasing,  and  not  at  all  troublesome  in  the 
sunlight. 

We  make  these  finishes  cheaper  simply  because,  not 
requiring  the  straight-grain  finish  surface,  it  requires  on  our 
part  less  labor,  and  we  decided  to  let  our  patrons  have  the 
benefit. 


Fig.  No.3.-ENGINEERS'  TRANSIT  No.  I  b. 


ENGINEERS'  TRANSIT  NO.  1  B. 

Fig.  No.  3  is  a  cut  of  a  complete  Engineers'  Transit  in 
every  way  similar  to  No.  1  A.  It  differs  slightly  from  cut. 
We  make  it  now  with  base  of  standards  reinforced. 

Its  dimensions  are  exactly  as  in  No.  1  A,  viz. :  6/4-inch 
horizontal  circle  ;  two  double  verniers  reading  to  30" ;  grad- 
uations on  brass,  silvered  ;  shades  over  verniers  ;  magnetic 
needle,  \%  inches  long;  radial  clamps  and  compensating 
tangents;  adjustment  for  the  vertical  plane  of  telescope; 
telescope  n  inches'long,  clear  and  powerful ;  i /4-inch  clear 
aperture ;  objects  seen  erect ;  split-leg  tripod. 

Mahogany  box  containing  sun  shade,  wrench,  plumb 
bob,  reading  glass,  and  two  adjusting  pins. 

Complete  with  vertical  arc  or  circle  five  inches  in  diam- 
eter, and  double  vernier  reading  to  single  minutes. 

Price $185  oo 

EXTRAS. 

Fixed  stadia  wires $  3  oo 

Adjustable  stadia  wires 10  oo 


Fig.  No.  4.-ENGINEERS'  TRANSIT  No.  I  c. 


ENGINEERS'  TRANSIT  NO.  1  c. 

Fig.  No.  4  is  a  cut  of  Transit  No.  1  c,  our  latest  model. 
It  is  really  a  magnificent  instrument,  capable  of  doing  the 
most  accurate  work.  In  cut  it  is  shown  with  verniers  at 
90°  from  the  line  of  sight,  or  between  the  standards.  When 
desired,  however,  we  place  them  at  an  angle  of  30  ,  or 
directly  in  the  line  of  sight. 

The  position  at  90°,  however,  has  this  advantage,  that  it 
admits  of  a  longer  level  on  the  plate,  which  is  desirable. 

It  has  a  horizontal  limb  634  inches  in  diameter ;  two 
double  verniers  reading  at  30"  ;  vertical  limb,  five  inches  in 
diameter,  with  a  double  vernier  reading  to  single  minutes  ; 
all  graduations  on  solid  silver;  magnetic  needle,  5)^  inches 
long ;  radial  clamps  with  compensating  tangent  screws ; 
ground  glass  shades  over  verniers  ;  5^-inch  sensitive  spirit 
level  to  Telescope. 

The  Telescope  is  from  n  to  12  inches  long,  very  clear 
and  powerful;  clear  aperture  of  object  glass,  from  iK  to 
i%  inches;  improved  eye-piece;  fixed  stadia  w7ires. 

We  must  strongly  recommend  this  instrument  to  those 
who  do  not  wish  a  Transit-Theodolite  for  the  most  accu- 
rate work. 

Price,  complete,  as    above $220  oo 

Without  vertical  arc  or  circle,  but  with  level  and 

clamp  to  Telescope 205  oo 

Plain 190  oo 


L'4 


EXTRAS    TO    TRANSIT    NO.    I   C. 

Gradienter    screw $500 

Variation  plate     .     .     .     .    ...     .     ...     .     ...  10  oo 

Adjustable  stadia  wires 7  oo 

Fixed  reading  glasses  for  reading  horizontal  limb  10  oo 

Fixed  reading  glass  for  reading  vertical  limb  .     .  ^  oo 

Two  reading  glasses  to  vertical  limb    ....  8  oo 
Two  double  verniers  to  vertical   limb,  reading  to 

30",  graduations  well  protected X7  5° 

Striding    level '75° 

Striding  level  fixed  to  arm  carrying  the  two  ver- 
niers of  vertical  limb 15  oo 

Arrangement  for  offsetting 4  oo 

Three  leveling  screws  instead  of  four     ...  75° 

NOTE. — We  also  make  this  instrument  with  a  6  or  y-inch 
striding  level  to  Telescope  instead  of  the  usual  fixed  level. 
This  can  be  attached  to  Telescope  whether  the  latter  is  in 
a  normal  position  or  reversed.  Price,  extra,  $25  oo.  When 
desired,  we  can  provide  this  instrument  with  a  solar  attach- 
ment. 


25 
ENGINEERS'  TRANSIT  NO.   2. 

We  did  not  deem  it  necessary  to  have  a  cut  made  for  this 
instrument,  it  being  essentially  the  same  as  our  No.  1  c, 
with  the  exception  of  size  and  weight. 

No.  2  is  a  very  carefully  and  perfectly  made  instrument. 
The  Telescope  is  large  and  powerful  enough  to  admit  ordi- 
nary stadia  measurements,  and  horizontal  limb  large 
enough  to  admit  of  the  readings  to  single  minutes  with  the 
utmost  ease.  It  is  very  efficient  for  good  railroad  work, 
general  land  surveying  and  mining  purposes.  Its  lightness 
makes  it  very  desirable  in  many  instances,  and  it  is  strong 
enough  to  admit  of  the  attachment  of  an  auxiliary  side  or 
top  Telescope  without  undue  strain. 

The  dimensions  are:  Horizontal  limb,  five  inches,  with 
two  double  verniers  reading  to  single  minutes ;  magnetic 
needle,  3^  inches;  Telescope,  9  to  10  inches;  clear  aper- 
ture iy&  inch. 

Weight  of  Instrument,  about  9  Ibs.  ;  weight  of  tripod, 
61A  Ibs. 

Price  of  Instrument  with  graduations  on  solid  silver,  and 
fixed  stadia  wires  : 

Plain $186  oo 

With  clamp  and  level  to  Telescope       ....  200  oo 
Vertical  arc  or  circle,  5-inch  double  vernier  read- 
ing to   minutes 215  oo 

EXTRAS  TO  TRANSIT  NO.     2. 

Gradienter  Screw $  ^  oo 

Adjustable  Stadia  Wires 7  oo 

Variations    Plate 10  oo 

Arrangement  for  offsetting 4  oo 


26 

EXTRAS  TO  TRANSIT  NO.   2,   FOR  MINING  PURPOSES. 

Striding  Level $17  50 

Lamp  with  ground  lens,   for  the  illuminating  of 

the  cross  wires  . 6  oo 

Lampholder  attached  to  standards 2  50 

Reflector  for  illuminating  the  cross  wires  ...  3  oo 

Diagonal   Ocular 1600 

Prism 6  oo 

Detachable  Side  Telescope 30  oo 

Detachable  Top  Telescope 50  oo 

Extension  Tripod 15  oo 

Plummet  Lamp 7  50 

Stadia  Wires,  adjustable 7  oo 

Gradienter  Screw 5  oo 

This  Instrument  can  also  be  provided  with  solar  attach- 
ment. 


27 
MOUNTAIN     TRANSIT. 

After  many  inquiries  and  some  suggestions  of  eminent 
Engineers,  we  decided  to  give  a  special  study  to  this  most 
convenient  of  Engineering  Instruments,  with  the  result  that 
we  decided  to  manufacture  two  sizes  ;  one  with  horizontal 
limb,  4>£  inches  in  diameter,  and  the  other  4  inches. 

The  former  is  a  little  heavier  (7  Ibs.),  but  its  very 
weight  gives  it  the  advantage  of  being  steadier  in  windy 
climates  (where  they  are  generally  used),  and  for  mining 
purposes,  will  admit  of  a  side  Telescope  and  all  accessories 
as  described  in  Transit  No.  2. 

The  smaller  has  the  advantage  of  being  lighter,  and  con- 
sequently more  portable  (although  still  very  strong).  All 
the  above  extras  would  be  a  great  strain  upon  it.  They  are 
styled  No.  3  A,  and  No.  3  B,  and  are  essentially  similar  to 
our  No.  1  A,  except  in  size.  They  are  very  carefully  and 
perfectly  made. 

No.  3  A  has  a  horizontal  limb  4%  inches ;  two  double 
verniers  reading  to  single  minutes ;  ground  glass  shades 
over  verniers  ;  vertical  limb  4  inches  ;  double  vernier  read- 
ing to  single  minutes  ;  all  graduations  on  solid  silver  ;  mag- 
netic needle,  3^  inches  long;  Telescope,  S%  inches  long; 
clear  and  powerful  erecting  or  inverting  eye  piece  ;  iM- 
inch  clear  aperture  ;  4-inch  sensitive  level  to  Telescope,  and 
2-inch  level  on  plate ;  shifting  center,  and  radial  clamps 
with  compensating  tangent  screws ;  extension  tripod. 

Mahoganybox  containing  all  appendages,  as  in  our  larger 
Transits,  and  provided  with  shoulder  strap. 

Price,  complete,  as  above $200  oo 

Transit  No.  3  A  can  also  be  provided  with  solar  attach- 
ment. 


Fig.  No.  5.-MOUNTAIN  TRANSIT. 


29 

EXTRAS    TO    TRANSIT  NO.    3  A. 

Fixed    stadia   wires $300 

Adjustable    stadia  wires 10  oo 

Prism  and  colored  glass  for  solar  observations  . 

Leather  cover  over  box 5  oo 

EXTRAS  TO  TRANSIT  NO.    3  A,   FOR  MINING  PURPOSES. 

Striding  level $   17  50 

Lamp   with    ground    lens  for  illuminating   the 

cross  wires 6  oo 

Lamp  holder  attached  to  standards 2  50 

Reflector  for  illuminating  the  cross  wires   .  3  oo 

Prism 6  oo 

Detachable  side  Telescope  ...."....  30  oo 

Plummet  lamp 75° 

No.  3  B  has : 

Horizontal  limb,  4  inches :  two  double  verniers  reading 
to  single  minutes  ;  vertical  limb,  4  inches  ;  double  vernier 
reading  to  minutes ;  graduations  on  solid  silver ;  ground 
glass  shades  over  verniers ;  magnetic  needle  2%  inches 
long ;  Telescope  8  inches  long,  clear  and  powerful ;  erect- 
ing or  inverting  eye  peice  ;  4-inch  sensitive  level ;  radial 
clamps,  and  compensating  tangent  screw  ;  extension  tripod, 
etc. 

EXTRAS  TO  NO.    3  B. 

Stadia  wires,  fixed $300 

Stadia  wires,  adjustable 10  oo 

Leather  cover   over  box 5  oo 


31 
WYE     LEVEL    NO.     i. 

This  Level  we  consider  the  most  improved  form.  The 
leveling  plate  is  of  the  best  hard  metal,  provided  with  quick- 
leveling  movement.  The  bar  is  of  hard  brass,  cast  hollow, 
and  provided  with  very  strong  ribs.  The  wyes  are  made 
of  the  best  hard  metal.  We  make  our  wyes  now  in  our 
improved  model,  as  shown  in  cut  of  Level  No.  2  ;  8-inch 
sensitive  spirit  level ;  Telescope  provided  with  stout  rings  of 
hard  bell  metal ;  and  with  a  stop  to  readily  set  wires  in  a 
horizontal  or  perpendicular  position;  object  glass  i3/$  to 
i  J  inches  aperture,  very  clear  and  powerful,  with  field  of. 
view  large  and  flat ;  line  of  collimation  guaranteed  true  for 
all  distances  ;  radial  clamp  and  compensating  tangent  screw  ; 
instrument  packs  whole. 

Mahogany  box  containing  wrench,  screw-driver,  two 
adjusting  pins,  and  the  sun  shade  of  Telescope.  Split-leg 
tripod. 

We  make  this  Level  in  three  sizes,  viz. :  18,  20  and  22- 
inch  lengths  of  Telescope ;  weight  of  instrument,  about 
10^  Ibs. 

Price. 

iS-inch  wye  level,  as  above $I25  °° 

20-inch     "          "  "  ..;....        132  50 

22-inch    "         "  ........        140  oo 


EXTRAS  TO  WYE  LEVEL. 

Centers  made  of  hardened  steel $     7  50 

Fixed  stadia  wires 3  oo 

Adjustable  stadia  wires 10  oo 

NOTE. — For  convenience  in  reading  the  bubble  in  soft 
ground,  without  changing  position,  we  can  furnish,  when 
so  desired,  to  our  leveling  instrument,  a  mirror  with 
universal  joint,  at  an  extra  expense  of  $10.00. 


33 


WYE     LEVEL     NO.     2. 

Level  No.  2  has  the  same  quality  and  sizes  as  No  i, 
except  that  it  is  not  made  quick-leveling.  The  center  plate 
is  similar  to  that  of  our  Transits  ;  otherwise  it  has  the  same 
bar,  and  the  same  radial  clamp.  The  wyes  are  our  improved 
model,  which  will  be  found  the  strongest  and  most  con- 
venient made,  there  being  no  pins  to  get  lost,  and  the  clips 
cannot  possibly  get  loose.  We  have  now  adopted  this  system 
in  all  of  our  levels. 

All  other  dimensions  are  the  same  as  in  No.  i,  with  same 
fine  Telescope  provided  with  dust  protection  over  slide. 
(Not  shown  in  cut). 

Price. 

1 8-inch $120  oo 

2O-inch 127  50 

22-inch 135  oo 

Extras  same  as  No.  i. 


35 


WYE     LEVEL     NO.     3. 

This  is  a  very  light,  portable  level,  and  at  the  same  time 
very  strong.  It  has  all  the  improvements,  as  radial  clamp, 
with  compensating  tangent ;  6£-inchfme  spirit  level ;  i6-inch 
powerful  Telescope,  with  large,  flat  field  of  view;  objects 
seen  erect.  The  Telescope  has  rings  of  hard,  bell  metal ; 
split-leg  tripod.  This  Level  is  also  furnished  now  with  our 
improved  wyes. 

Price $100  oo 


37 


IMPROVED     ARCHITECT     LEVEL. 

This  instrument  was  designed  to  supply  a  long-felt  want, 
It  is  primarily  a  superior  Architect  Level,  but  able  to  do  at 
the  same  time  very  accurate  leveling  work.  It  has  a  very 
strong  reinforced  center  plate.  It  is  provided  with  a  4- 
inch  horizontal  circle,  graduated  to  degrees,  figured  from 
o  to  90°,  each  way,  and  is  read  to  five  minutes  by  a  ver- 
nier attached  to  the  spindle.  It  is  provided  with  radial 
clamp  and  compensating  tangent  screw  ;  a  6-inch  sensitive 
spirit  level ;  Telescope  15  or  16  inches  long,  clear  and  pow- 
erful;  object  glass  iH  to  i^-inch  clear  aperture;  field  of 
view  large  and  flat;  in  fact,  a  very  good,  reliable  instru- 
ment. 

In  mahogany  box,  price $75  oo 


38 


PRECISE     LEVELING     INSTRUMENT. 

NOTE. — We  are  now  designing  a  Level  of  Precision,  a 
cut  of  which  will  be  found  in  our  future  large  Catalogue. 
We  are  enabled,  however,  to  give  here  a  description. 

This  Level  will  differ  from  our  other  Levels  in  that  it  is 
always  made  with  three  leveling  screws  ;  it  has  a  horizontal 
circle  from  5  to  6  inches  in  diameter,  graduated  to  read  to 
30"  and  20" ;  graduations  on  solid  silver ;  radial  clamps 
with  compensating  tangent  screws  ;  the  bar  is  very  hard  and 
unyielding ;  wyes  of  very  hard  metal  with  agate  bearings  ; 
steel  center ;  front  wye  is  set  to  the  bar  very  firmly,  with  steel 
screws  in  steel  bearings,  and  has  a  balancing  front  move- 
ment; the  other  wye  is  adjustable  by  a  very  precise  micro- 
meter screw  with  graduated  head,  which  can  also  be  used  as 
a  gradienter ;  the  rising  and  depressing  of  the  telescope  is 
made  with  the  utmost  exactness. 

The  Telescope  has  an  aperture  of  i^-inches  or  more:  18 
inches  focus  ;  two  very  powerful  astronomical  oculars. 

The  spirit  level  is  of  an  improved  form  (fixed  astride), 
which  can  easily  be  taken  off  when  desired,  and  is  cham- 
bered to  regulate  the  length  of  the  bulb  ;  the  sensitiveness  of 
the  bulb  is  so  that  one  of  its  divisions  corresponds  to  from 
2  to  5  seconds  of  arc  as  desired. 

Further  particulars  will  be  cheerfully  given  to  those  wish- 
ing them. 


PROF.    JOHNSON'S     EXTENSOMETER. 

AN    APPARATUS    FOR  MEASURING  THE  DISTORTIONS  OF  TEST 
SPECIMENS. 

Fig.  No.  10  is  a  cut  of  Prof.  J.  B.  Johnson's  Extenso- 
meter. 

It  consists  of  two  brass  collars  having  22-inch  openings, 
which  are  held  upon  the  specimen  to  be  tested  by  three 
pointed  steel  screws,  one  of  which  has  a  spring  bearing. 

To  each  collar  is  attached  a  graduated  circle,  four  inches 
in  diameter,  carrying  upon  its  face  a  balanced  vernier 
needle.  The  needle  is  rigidly  attached  to  an  axle  that  turns 
very  freely,  but  without  any  lost  motion,  on  which  is 
arranged  a  perfectly  true  cylinder  exactly  one-half  inch  in 
circumference. 

An  elastic  steel  armature  is  rigidly  attached  to  each  col- 
lar, and  has  a  friction  bearing  with  spring  pressure  on  the 
rolling  cylinder  upon  the  other  collar.  These  cylinders  and 
armatures  are  symmetrically  mounted  on  the  two  opposite 
sides  of  the  bar  to  be  tested,  so  that  any  warping  or  bend- 
ing of  the  bar  under  test  affects  the  movement  of  the  two 
cylinders  equally,  but  in  opposite  directions,  and  the  mean 
of  the  two  readings  is  always  free  from  the  effects  of  such 
movements. 

The  circles  are  graduated  into  5°°  subdivisions,  and  the 
small  vernier  at  the  end  of  the  index  needle  reads  to  one- 
tenth  of  one  of  these  spaces,  so  that  the  smallest  reading  of 
the  instrument  corresponds  to  one-ten-thousandth  of  an 
inch. 

Readings  are  easily  made  to  one-twenty-thousandth  of  an 
inch  with  perfect  accuracy. 


Fig.  No.  IO.-PROF.  JOHNSON'S  EXTENSOMETER. 


41 

The  advantages  of  this  apparatus  are  : 

1.  It  is  equally  well  adapted  to  horizontal  and  vertical 
positions  of  the  test  bar. 

2.  It  gives  the  average  stretch  of   both  sides  of  the  bar, 
and  so  eliminates  all  unsymmetrical  distortions  of  the  bar. 

3.  It  is   equally  well  adapted  to  tension  or  compression 
tests. 

4.  It  is  adapted  to  all  lengths  of  specimen  above  three 
inches  of  tested  section,  by  simply  substituting  new  lengths 
of  side  bars,  three  sets  of  which  acccompany  each  instru- 
ment. 

5.  It  gives  the  distortions  beyond  the  elastic  limit  as  well 
as  inside  that  limit,  with  equal  readiness,  by  continual  rev- 
olution of  the  index  hand 

6.  Both  the  apparatus  as  a  whole,  and  the  index  pointer 
are  at  all  times  in  equilibrium,  or  in  perfect  balance. 

7  The  collars  are  cut  and  hinged  so  that  they  can  be 
removed  before  rupture  occurs. 

8.  The  stretch  is  made  visible  to  the  eye  of  the  observer 
at  the  moment  of  its  occurrence,  and  the  observer  thus  notes 
when  this  movement  ceases  after  a  given  load  has  been  put 
on.  This  is  a  very  important  matter,  especially  for  stu- 
dents. 

This  instrument  is  guaranteed  to  do  all  that  is  here 
claimed.  The  greatest  care  is  taken  in  its  manufacture, 
and  each  instrument  is  tested  by  Prof.  Johnson,  and  goes 
out  with  his  certificate  as  to  its  accuracy. 

Price,  complete,  with  three  sets  of  elastic  steel  arma- 
tures, circles  graduated  on  silver,  and  Prof. 
Johnson's  certificate, $100 


Fig.  No.  II.-COLBY'S  TOPOGRAPHICAL  PROTRACTOR. 


43 


COLBY'S  TOPOGRAPHICAL  PROTRACTOR. 

This  perfect  instrument  was  designed  by  Mr.  B.  H. 
Colby,  an  Engineer  of  many  years'  experience  upon  Gov- 
ernment surveys. 

While  it  can  be  used  for  all  kinds  of  ordinary  protracting, 
it  was  especially  designed  for  the  plotting  of  angles  and  dis- 
tances by  polar  co-ordinates,  as  taken  by  the  ordinary 
method  of  stadia  surveying.  For  this  purpose,  this  pro- 
tractor is  without  a  rival,  either  in  speed  or  accuracy. 

It  is  made  in  three  pieces.  The  largest  piece  is  the  limb, 
L,  L,  L,  graduated  from  o  to  360°,  with  i5-minute 
divisions;  E,  E,  are  projections,  or  ear-pieces,  upon 
which  lead  weights  are  placed.  The  limb  has  four  indices, 
B,  B,  B,  B,  90°  apart,  by  which  the  protractor  is  oriented. 
A,  A,  A,  is  the  alidade,  perfectly  fitted  to  revolve  inside 
the  limb,  easily  and  writh  no  lost  motion.  G,  G,  are  indexes 
carried  by  the  alidade,  180°  apart.  To  the  bar  D,  of  the 
alidade,  is  attached  the  scale  S,  by  the  small  screws  and 
nuts.  N,  N,  the  scale  has  zero  mark  in  middle,  and  is 
graduated  both  ways.  It  can  be  taken  off  by  unscrewing 
the  nuts  N,  N,  and  a  scale  of  different  denomination  sub- 
stituted when  desired. 

A  groove  and  small  clips,  upon  underside,  hold  all  the 
parts  together.  A  slight  space  is  provided  for,  when  in 
use,  to  prevent  the  scale  rubbing  upon  the  paper. 

Too  much  cannot  be  said  of  the  merits  of  this  protractor. 


44 

We  make  it  of  German  Silver,  of  any  size  desired,  and 
graduate  scale  as  required.  Each  protractor  is  put  up  in 
handsome  case. 

Prices  are  as  follows : 

Price. 

12-inch  limb $  75  oo 

10    "       " 55  oo 

9    "       "  45  oo 

Extra  scales ,  each      ....  10  oo 


45 


COLBY'S  SLIDE  RULE  FOR  STADIA 
REDUCTIONS. 

GIVES    DIFFERENCES  OF    ELEVATION    BETWEEN    TWO    POINTS 

WHEN    DISTANCE-READING    AND    VERTICAL    ANGLE 

ARE     KNOWN. 

This  adaptation  of  the  slide  rule  was  designed  and  used 
by  Mr.  B.  H.  Colby,  engineer  in  charge  of  the  extensive 
topographical  surveys  made  by  the  City  of  St.  Louis.  It 
takes  the  place  of  tables  or  diagrams,  and  is  much  superior 
to  either. 

In  practice  it  has  been  found  to  be  about  three  times  as 
rapid  as  the  tables,  and  almost  as  accurate. 

It  will  give  25  per  cent  of  the  differences  met  with  in 
stadia  work  correctly  to  the  nearest  thousandth  of  a  foot; 
50  per  cent  to  the  nearest  hundredth  of  a  foot,  and  all 
differences  to  the  nearest  tenth  of  a  foot. 

It  saves  much  mental  labor  of  a  grinding  nature,  and 
can  be  used  by  any  person  of  ordinary  intelligence  after  a 
few  minutes  instruction. 

The  scales  are  4^  feet  long,  mounted  upon  wooden 
frame  and  slide  as  shown  in  cut.  The  upper  graduation 
is  a  logarithmic  scale  repeated  twice,  the  logarithms  being 
affected  by  a  constant  coefficient,  whose  value  was  taken 
so  as  to  give  correctly  to  the  nearest  tenth  of  a  foot,  all 
differences  of  elevation  commonly  met  with  in  topograph- 
ical surveying  with  stadia. 

The  lower,  or  arc  scale,  is  graduated  up  to  twenty 
degrees. 


47 

In  using  the  scale,  the  graduation  mark  on  the  upper 
scale  representing  the  distance,  is  brought  coincident  with 
the  zero  mark  on  the  lower  scale,  the  difference  in  vertical 
height  can  then  be  read  from  the  upper  scale  at  the  point 
coincident  with  the  required  vertical  angle  on  the  lower 
scale. 

In  the  Journal  of  the  Association  of  Engineering 
Societies  (January,  1893),  Prof.  J.  B.  Johnson,  of  Wash- 
ington University,  says:  "  The  slide  rule  here  described 
has  been  adopted  for  the  use  of  the  students  in  the 
University,  and  I  am  free  to  say  that  it  furnishes  the  most 
expeditious  method  I  have  ever  seen  for  reducing  stadia 
observations." 

Colby's  Slide  Rule  is  now  being  adopted  upon  topo- 
graphical surveys  throughout  the  country,  and  must  soon 
be  recognized  as  an  indispensable  adjunct  to  the  stadia. 

Price       .      .      .      .  $18.00 


Besides  the  scientific  instruments  illustrated  in  this  pam- 
phlet, we  are  prepared  to  manufacture  others  of  almost 
any  description.  Among  these  may  be  mentioned  cathe- 
tometers,  telemeters,  spectrometers,  etc. 

The  cathetometer  is  an  instrument  designed  to  measure 
with  precision  minute  differences  in  height. 

It  consists  principally  of  a  very  solid  tripod  case,  usually 
made  of  brass,  supporting  a  standard  made  of  brass ;  the 
standard  usually  consists  of  two  brass  tubes  to  which  is 
very  firmly  attached  a  dove-tailed  bar  with  a  scale  fixed 
in  the  center  and  graduated  as  may  be  required ;  upon 
this  bar  slides  a  carriage  ;  a  small  leveling  instrument  pro- 


48 

vided  with  a  fine  telescope  and  the  usual  cross  wires  is 
secured  to  this  carriage,  which  has  also  a  vernier  scale 
and  is  balanced  by  lead  weights  suspended  within  the 
brass  tubes. 

A  movable  clamping  piece  is  fitted  below  the  carriage 
and  is  fixed  at  any  point  required,  by  a  screw.  A  micro- 
meter screw  passes  through  the  center  of  the  clamping 
piece ;  this  screw  has  a  large  head,  graduated  into  one 
hundred  parts,  and  having  an  index  at  its  side,  affords  a 
means  of  reading  a  very  small  movement  of  the  carriage 
as  it  is  carried  by  the  screw. 

The  scale  in  front  of  the  standard  is  read  by  the  vernier 
fixed  to  the  carriage. 

The  column  has  an  apparatus  by  which  it  can  be  made 
perfectly  plumb.  This  operation  is  effected  by  leveling 
screws  in  base ;  said  base  having  three  long  arms,  forming 
the  tripod. 

NOTE. — We  are  now  making  a  design  to  simplify  the 
above  method  of  construction,  and  consequently  reduce 
the  cost  of  manufacture. 

To  those  interested  in  the  above-mentioned  instruments, 
further  description  and  prices  will  be  cheerfully  given 
when  required.  We  will  endeavor  to  describe  them  more 
completely,  and  possibly  illustrate  them,  in  future 
catalogues. 


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